Troubleshooting Tip: Ring Crush Test

The ring crush test is a method for measuring the edgewise crush resistance by forming the paper into a cylinder and applying a crushing force to the edge. For more information refer to TAPPI T818.

Linerboard products are subjected to crushing forces in handling, storage and shipment. Knowledge of the edgewise compression strength is useful in controlling the manufacturing process, and in providing an indication of the compression resistance to be expected in the finished product.

Here is a list of actions that may improve Ring:

1.Rush the sheet more or drag the sheet less.
2.Optimize refining. There should a sweet spot for ring crush. There may be times when the fiber is over refined.
3.Dry up the sheet more if possible.
4.Increase basis weight.

Realize if you dry up the sheet to improve ring crush, it may reduce your tensile strength, or burst strength. Also, increasing basis weight will increase the cost of production. However, it is better than producing broke, or reject paper.  The best method for optimizing refiners is to talk to your senior stock prep operators. If they've been around for a while, they generally have a pretty good idea where to start based off refiner plate wear and the grade of paper. When adjusting the rush/drag, be sure to get your machine tenders' input. Also make sure to pay attention to the draws as this can have an effect on them, you don't want to have a break due to lack of attention to detail.